You cannot beat this ambi-magazine release for the price - lefties rejoice! - SIG SAUER Ambi Mag Catch Assy, M400, 516

The Sig's release 'button' is very close to where the magazine release is on the opposite side of the rifle. I have a Strike 'enhanced' bolt release and this mag catch doesn't interfere with it. In the end, I kept the Troy part, (which was purchased at the same time as the Sig part) but have purchased two more Sig ambi catches for my various AR rifles.
It functions as well as the more expensive parts from other makers. One VERY little thing; the release lever pivots directly against the receiver and may leave little marks - If you have a priceless finish on your rifle, that's your problem. In the end; this release will set you back only 17 dollars and it's made as well as any mil-spec part. All I can say is give it a try!